The invention pertains to a process and to a device for the production of a catalyst comprising a monolith with a polygonal cross section. A polygon in the present context is understood to mean a shape with multiple sides, the corners of which are rounded.
Exhaust gas catalysts for motor vehicles consist of a central, rod-shaped, ceramic honeycomb, called a “monolith”, through which many fine channels pass in the longitudinal direction. The monolith is surrounded by a jacket of metal sheet or plate, especially of special steel, between which and the monolith a layer of so-called expanded matting of mineral fiber is placed. The jacket made of metal sheet or plate must be seated very tightly around its entire circumference to ensure that the impact-sensitive material of the monolith is not damaged, especially during the operation of the motor vehicle; so that no annoying rattling noises occur; and so that the seal between the monolith and the jacket made of metal sheet or plate is preserved. It must also be taken into account that the jacket made of metal sheet or plate is cold when not in operation but very hot during operation. As a result, the jacket made of metal sheet or plate is subject to a certain amount of expansion and shrinkage around the circumference.
These types of catalysts, obviously for cost reasons, have been produced so far only with circular cross sections, for it is generally known that circular cross sections are the easiest to seal. Stricter legal regulations and the demand for better utilization of the space available in the motor vehicle, however, have made it appear desirable today to produce catalysts which deviate from the circular form and which in particular have a polygonal shape as defined above. But even when a shape such as this is used, the jacket made of metal sheet or plate must still wrap so tightly around the monolith that the expanded matting will still provide a sufficiently strong, leak-proof seat and simultaneously offer a certain amount of damping.